diff --git a/lib/make/fonts.js b/lib/make/fonts.js
index f025bec..aeb7f45 100644
--- a/lib/make/fonts.js
+++ b/lib/make/fonts.js
@@ -34,6 +34,10 @@ make.font = {
       make.unit.percent()
     ])
   },
+  relativeSize: function () {
+    let value = random.number(8)
+    return random.item(['', '+', '-']) + value
+  },
   genericFamily: function () {
     return random.pick(['serif', 'sans-serif', 'cursive', 'fantasy', 'monospace'])
   },